Negative association of neuroticism with brain volume ratio in healthy humans

Background: Brain volume decreases with normal aging. We sought to determine whether, in addition to age, individual differences in stress reactivity (i.e., neuroticism) would also predict reductions in brain volume. Methods: Brain volume ratios were calculated for a sample of 86 healthy volunteers, based on segmented brain volumes taken from T1-weighted magnetic resonance imaging and corrected for intracranial volume. Standardized self-reported measures of dispositional neuroticism were concurrently obtained by administering the Revised NEO Personality Inventory. Results: After statistically controlling for age and sex, neuroticism showed a significant negative association with the ratio of brain to the remainder of the intracranial volume, but was not related to intracranial volume itself. In particular, subfactors of neuroticism related to the chronic experience of arousing negative emotions were associated with reduced brain ratio. Conclusions: These results suggest that individual differences in stress reactivity contribute to reductions in brain volume observed during adulthood.